Elimination of air and vapors from a centrifugal pump



Aug. 21, 1962 J. J. PACEY ETAL ELIMINATION OF AIR AND VAPORS FROM ACENTRIFUGAL PUMP 2 Sheets-Sheet 1 Filed Dec.

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I mm Aug. 21, 1962 J. J. PACEY ETAL ELIMINATION OF AIR AND VAPORS FROM ACENTRIFUGAL PUMP 2 Sheets-Sheet 2 Filed Dec.

INVENTORS JOHN J. PACAIY G0RG D. ROBINSON J)?- BY 06,4. W14

A T TMNE YS 3,058,008 ELATION on AIR AND vAPoRs FnoM A cnNTnn UnAL PUMPJohn J. Pacey, Springfield, and George D. Robinson, Jr.,

Agawam, Mass, assignors to Gilbert 8: Barker Manufeaturing tlompany,West Springfield, Mass, a corporation of Massachusetts Filed Dec. 30,1958, Ser. No. 783,842 4 Claims. (Cl. 103-413) The present inventionrelates to centrifugal pumps and more particularly to improved means foreliminating air, vapor or gases from the pumping system.

The prime object of the invention is to provide improved and simplifiedmeans for eliminating air from a centrifugal pumping system so as toprime the pump or to maintain the pump in operation when a substantialamount of air becomes entrained in the suction line of the centrifugalpump.

Another object of the invention is to accomplish the above ends whenworking against high back pressures or pressure heads in the dischargeline in a centrifugal pump.

The above and other related objects of the invention as well as thenovel features thereof will be apparent from a reading of the followingdescription of the disclosure found in the accompanying drawings and theparticular novelty thereof pointed out in the appended claims.

In the drawings:

FIG. 1 is an elevation showing a centrifugal pumping system in which thepresent invention is incorporated;

FIG. 2 is a view, on an enlarged scale, of the centrifugal pump unititself as shown in FIG. 1 (generally indicated by numeral 10) with partsbroken away and in section;

FIG. 3 is a section, on a further enlarged scale, taken on line III-IIIin FIG. 2;

FIG. 4 is a perspective view, with portions broken away and on anenlarged scale, of an air separator seen in FIG. 1;

FIG. 5 is a section taken on line V-V in FIG. 4, and

FIG. 6 is a section on a further enlarged scale, taken on line VIVI inFIG. 4.

The overall organization of a pumping system embodying the presentinvention may be seen by referring to FIG. 1 in the drawings. Basically,this system comprises a centrifugal pump 18, a positive displacementpump 12 and an air separator 14. A suction pipe 16 extends from a liquidsource (not shown) to the centrifugal pump while a discharge pipe 18provides for delivery of the liquid to whatever point may be desiredwithin the capabilities of the pump 10.

One inherent shortcoming of centrifugal pumps is their inability to drawany substantial vacuum pressure in a gaseous medium. Thus it is that acentrifugal pump must be primed with liquid before it will becomeoperative. This problem has been overcome in the past by the provisionof a positive displacement priming pump for initially creating a vacuumin the suction line of a centrifugal pump to draw liquid from a remotesource at a lower level and thereby prime the pump. The function andpurpose of the priming pump 12 is also the same in the present instance.However, in accordance with the objects of the invention, the pump 12 ischaracterized by its efiiciency and its effectiveness in priming wherethere is a high head or back pressure in the discharge pipe 18.

The pump 10 comprises a frame 21) (FIGS. 1 and 2) which is mounted on abase 22. A housing 24 is secured to the frame 24 and is provided with acentral inlet communicating with the suction pipe 16 and a tangentialoutlet communicating with the outlet pipe 18. The housing 24 is closedoff by a plate 26 which provides a journal for a shaft .28 on which ismounted a vaned impeller 30.

3,85,888 Patented Aug. 21, 1952 In the preferred form of the invention,the priming pump 12 is also driven from the shaft 28 and comprises arotor 32 (FIGS. 2 and 3) keyed thereto. The rotor 32 is disposed withina housing 34 secured to the plate 26 which is sealed off at its oppositeend by a plate 35 to provide a closed chamber for the priming pump 12. Aslide or collar 36 encircles the rotor 32 and is slidably guided forvertical movement relative to the housing 34 by means of lugs 37 with aspring 38 yieldingly holding it in its lower position for reasons whichfurther appear. The rotor 32 is relieved on each of its radial faces toreceive thrust rings 39 against which blades 40 hear. The blades 40 arecarried by the rotor 32 andare axially slidable relative thereto. Theslide 36 at its top and bottom ends is flush with the plates 26 and 35to define a suction chamber 41 and a pressure chamber 43 on oppositesides of the shaft 28. The slide 36 is also relieved on opposite sidesof the shaft 28 to provide for communication with a suction tube 42 anda discharge tube 44 which communicate through passageways in the housing34 with the suction chamber 41 and pressure chamber 43 respectively. Theaction of the pump 12 as above described is well known and the rate orcapacity of the pump is dependent on the vertical position of the slide36 and the degree of eccentricity of the thrust rings 39 relative to theshaft 28.

Outwardly of the plate 38 is a bearing housing 46 (FIG. 1) for the shaft28 which extends therebeyond to a universal coupling 47 providing aconnection with the shaft of an electric motor 48. The motor 48 is forconvenience sake mounted on the base 22 and may be provided with anyform of electrical control desired. In any event for the purposes of thepresent invention, it is only necessary that the shaft 28 be powerdriven.

Although the impeller of the centrifugal pump 10 could rotate about avertical axis, certain advantages in the operation of the priming pumpare to be had from mounting the impeller for rotation about a horizontalaxis, as illustrated. Thus it will be seen that the suction tube 42(FIGS. 1 and 2) extends from the priming pump 12 to the top of the inletpipe 16. For convenience, the suction tube 42 is actually connected tothe top of an adapter 50 which is interposed between the pipe 16 and thepump housing 24, the adapter in essence being a part of the pipe 16.

When the pump 10 is started up by energizing the motor 48, the suctionpipe 16 must first be evacuated to draw liquid to the pump 10. Thisfunction is accomplished by the priming pump 12 which pulls air and/orvapors through the tube 42 to evacuate the pipe 16 and thereby pullliquid into the centrifugal pump housing 24. With the suction side ofthe priming pump 12 connected to the top of the suction pipe 16, primingof the pump 10 will be most efiiciently accomplished in that only air orvapors will be drawn into the priming pump 12. That is, there will be notendency for liquid to enter the tube 42 and thus the pipe 16 will beevacuated at maximum efliciency. Once the pipe 16 has been evacuatedsufiiciently to prime the pump 10, its centrifugal action will take overto pull liquid through the pipe 16 and discharge it through the pipe 18.With. the

prime established, liquid instead of air will be drawn through the tube42.

In order to take advantage of other features of the invention, it ispreferable that the priming pump discharge tube 44 be connected to theair separator 14 as indicated in FIG. 1. The air separator comprises acompositely formed closed vessel 52 (FIGS. 1 and 4) to which the tube 44is connected by appropriate fittings intermediate the height of thevessel. An air vent opening 54 (FIGS. 4 and 5,) is provided at the upper.end

of the vessel 52 and a liquid outlet 56 (FIG. 6) is provided at thelower end of the vessel 52. The air vent opening 54 takes the form of asimple hole formed in a plate 55 (FIGS. 4 and 5) at the upper end of thevessel 52 with a flange plate 57 providing means for mounting a pipe orconduit 58 which may extend to an appropriate location for discharge ofair and vapors which may be explosive or malodorous. The liquid outlet56 is formed in a fitting 59 (FIGS. 4 and 6) threaded into the bottom ofthe vessel 52. The fitting 59 provides means for connecting one end of areturn line 60 to the vessel 52. The return line 60 extends to thesuction pipe 16, being connected to the adapter 50.

Valve means are provided for the air opening 54 and the liquid outlet 56respectively. 'In the former instance, a fiat resilient metal ribbon 62(FIGS. 4 and 5) is secured at one end to the Wall of the vessel 52immediately below the opening 54. The ribbon valve 62 is curved inwardlywith its other end being secured to a block 64 atop a verticallydisposed rod 66. It will be appreciated that as the rod 66 is movedupwardly, the ribbon valve 62 will be flattened against the inner wallof the vessel 52 and seal olf the air opening 54. A second ribbon valve'62 is also attached to the block 64. The ribbon valve 62' could beemployed to seal off a second air vent opening on the opposite side ofthe vessel 52, but in the present case it is merely being used tobalance the lateral thrust of the valve 62.

The valve means for the liquid outlet 56 preferably take the form of aneedle valve cone 68 (FIG. 6) formed on the lower end of the rod 66which seats in the opening 56. It will be seen that the lower end of therod 66 is guided for vertical movement by an upstanding skirt 70 formedon the fitting 59 and that the holes 72 are provided to insure flow ofliquid from the bottom of the vessel 52 to the liquid outlet 56. It willalso be seen that the upper end of the rod 66 is guided for verticalmovement by a spider 71 (FIG. 4).

A float 74 is mounted on the rod 66, being axially fixed thereon bycotter pins 76. When liquid rises in the vessel 52, the rod 66 israised, lifting the needle valve 68 off its seat and at the same time orshortly thereafter closing the ribbon valve 62. For present purposes itwould also be feasible to have an arrangement wherein the air ventopening is closed before the liquid outlet is opened when the level ofliquid rises in the vessel 52, the prime consideration, in accordancewith other aspects of the invention, being that the valve 62 be closedbefore the level of the liquid is sufiiciently high for foam thereon toescape through the opening 54. In other words the opening 54 must bespaced a substantial distance above the level of liquid to allow forcollapse of foam so that only air or vapors escape through the pipe 58.

The operation of the priming pump 12 in combination with the airseparator 14 is as follows: When the motor 48 is energized, the pump 12is set into operation and immediately begins to draw air through thesuction tube 42 thereby evacuating the suction pipe 16. At this point,it will be noted that a check valve 78 may be provided in the dischargepipe 18 to insure evacuation of the suction pipe 16 and also to enable ahigh head to be maintained at all times on the discharge side of thecentrifugal pump 18 when such is necessary or desirable.

Air or vapor is thus drawn from the pipe 16 and pumped by the positivedisplacement priming pump 12 to the air separator 14. When starting up,there will be little or no liquid in the vessel 52 so that the liquidoutlet 56 will be closed while the air opening 54 will be open. Thus theevacuated air will be discharged to atmosphere through the pipe 58. Thisaction continues until suflicient liquid is drawn into the suction pipe12 to prime the pump 10. It will be noted that the priming action of thepump 12 is nowise affected by the back pressure in the discharge pipe18. Thereafter, once the centrifugal pump 10 is operative, the primingpump 12 will begin to draw liquid from the suction pipe 16 and dischargeit into the vessel 52 (FIG. 1). As the level of liquid rises in thevessel 52, the float 74 (FIGS. 4-6) Will be raised, first opening thevalve 68 allowing liquid to flow through the return line 60 back to thesuction pipe 12. Further rise of the liquid level will cause the ribbonvalve 62 to close off the air opening 54 and, after priming, the normalcondition of the air separator is for the air opening to be closed andthe liquid outlet to be open. Thus it is that a small amount of liquidis bypassed from the centrifugal pump 10 during its normal operation.

The amount of liquid bypassed is minimized by making the outlet opening56 sufliciently small so that liquid will not flow therethrough as fastas it is delivered into the vessel 52 by the pump 12. This means that apressure is built up in the vessel 52 which is a back pressure effectiveon the pump 12 and built up in the discharge chamber 43 of the pump 12(FIG. 3). This back pressure is transmitted through a passageway to thebottom lug 37 of the slide 36 and tends to raise the slide against theaction of the spring 38. As the slide is raised, the eccentricity ofthrust rings 39 is reduced and the capacity of the pump 12 is likewisereduced. Thus a balance is obtained wherein the rate of flow into thevessel 52 equals or approximates the rate of how through the liquidoutlet 56. This balanced condition is of course obtained by having theproper strength in spring 38 so that the slide 36 will rise in responseto the proper back pressure built up in the vessel 52.

While workable systems may be developed without any substantial backpressure in the vessel 52, the described relation is preferred. Thuswhen there is a back pressure, there is a minimum tendency for foam toform and the flow of liquid through priming pump 12 and the airseparator 14 is continuous.

The air elimination means above-described for evacuating the suctionpipe 16 in initially priming the pump 10 is equally eifective inscavenging air and vapors which for one reason or another may becomeentrapped in the suction pipe 16 during normal operation of the pump 10.Thus air or vapors will rise to the top of the tube 16 and be drawntherefrom by the priming pump 12. These scavenged gases are forced intothe closed vessel 52 causing a gradual lowering of the liquid leveltherein. When the float 74 is lowered sufficiently, the ribbon valve 62will open the air opening 5'4 and the scavenged gases will be exhaustedto atmosphere. Thereafter, as further liquid is pumped into the vessel52, the ribbon valve 62' will close and the condition of the airseparator 14 will revert to that above described for the normaloperation of the pumps 10 and 12. If a really large amount of air isentrapped in the suction pipe 16, the action of the air separator isessentially the same except the level of liquid in vessel 52 will morethan likely drop far enough so that needle valve 68 Will close off theliquid outlet 56. Thus there is always a safeguard against air beingbled back to the suction pipe 16 through the return line 60.

Having thus described the invention, what is claimed as novel anddesired to be secured by Letters Patent of the United States is:

l. The combination of a centrifugal pump having a power driven shaft onwhich is mounted an impeller, a horizontal suction pipe leading to saidimpeller, an adapter interposed between said suction pipe and saidcentrifugal pump and a variable capacity priming pump, a suction tubeleading from the top of said adapter to the suction side of said primingpump, and an air sepa rator, said air separator comprsing a closedvessel of substantial height having an air opening at its upper end anda liquid outlet in its lower wall, a discharge line for dischargingfluid from said priming pump into said vessel, said discharge line beingconnected to said vessel at a point intermediate its height, a ribbonvalve for closing said air opening, said ribbon valve being connected atone end to the wall of said vessel immediately beneath said air opening,a vertically disposed rod within said vessel to the top of which theother end of said ribbon valve is connected, said vertically disposedrod having a needle valve formed on its lower end for closing saidliquid outlet, a return line connecting said liquid outlet with thesuction pipe of said centrifugal pump, said liquid outlet being of asize less than that required to pass liquid at the normal rate ofdelivery of liquid into said vessel by said priming pump wherebypressure will be built up in said vessel and means responsive to saidpressure in said vessel for reducing the capacity of said priming pumpto balance the rate of discharge of liquid into said vessel inaccordance with the rate of flow of liquid through said liquid outlet, afloat secured to said vertical rod and operable to raise the needlevalve to open said liquid outlet and also raise the said other end ofsaid ribbon valve to close oil? said air opening Whenever the liquid insaid vessel'rises above a given level which level is spaced asubstantial distance beneath said air opening sufficient to prevent anyfoam which might build up in the liquid in said vessel from reachingsaid air opening, said rod being free to follow said float as it followsthe height of said liquid below said given level to thereby close saidliquid outlet and open said air opening.

2. The combination of a centrifugal pump, a variable capacity primingpump having an inlet line from the suction side of the centrifugal pumpand a discharge line back to the said suction side, and an air separatorin said discharge line, said separator comprising a closed vessel withan air vent opening in its upper end and a liquid outlet spaced asubstantial distance beneath said air vent, valve means for opening andclosing said air valve, valve means for opening and closing said liquidoutlet, liquid level responsive means actuating both said valve meansfor closing said air vent While opening said outlet and for opening saidair vent while closing said outlet, the level of liquid suflicient tocause closing of said air vent being substantially below said vent inorder to block entrance of foam thereto, said separator vessel outletbeing of lesser size than said discharge line from the priming pump intothe vessel, and said priming pump having means responsive to pressure insaid vessel to reduce the capacity of the pump and balance the rate offlow into the vessel in accordance with the rate of flow from thevessel.

3. The combination of a centrifugal pump, a variable capacity primingpump having an inlet line and a discharge line connected to the suctionside of said centrifugal pump, and an air separator in the saiddischarge line, said separator comprising a closed vessel the inlet ofWhich is intermediate the top and bottom thereof and the outlet of whichis at the bottom, said outlet being of less size than required forreceiving liquid at the normal delivery rate of said priming pump, saidvessel having an air vent at the top substantially above said vesselinlet, a valve for said air vent and a valve for said vessel outlet,float means in said vessel controlling operation of said valves inresponse to the level of liquid therein for simultaneously opening onevalve while closing the other, said priming pump having means responsiveto pressure in said vessel to reduce the pumping capacity thereof.

4. The structure of claim 3 in which said float means includes avertically disposed rod extending upwardly in the vessel the top of saidrod being connected to said air vent valve and the bottom of said rodforming a valve to close and open said vessel outlet.

References Cited in the file of this patent UNITED STATES PATENTS1,551,362 Barton Aug. 25, 1925 1,591,388 Jennings July 6, 1926'1,890,317 Durdin Dec. 6, 1932 1,910,775 Saxe May 23, 1933 2,064,988iRisser Dec. 22, 1936 2,150,125 Nelson Mar. 7, 1939 2,313,773 SamiranMar. 16, 1943 2,318,264 Smith May 4, 1943 2,511,351 Laidley June 13,1950 2,535,583 Kroll Dec. 26, 1950 2,881,708 Wernert Apr. 14, 19 59

